Why is entire wall lit when a wall divides it in half?

Notice the light lighting up the entire face of the walls and getting inside the room despite half of the objects being blocked off by the wall.

Is this default behavior? If so, how can I fix it?

BTW, the lightmaps should be good on my objects. And the walls are all the same object, as well as the floor and roof panels.

Here is the picture from the inside where the light leaks.
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Here is the picture from the outside.

Solved the issue.

It was because I had the lighting mode on preview. Putting it on production fixed it, as well as some other lighting issues I was having.